The present invention relates to an improved method of producing organic phosphorus compounds comprising halogens of the formulaXPR2(OR1)  Ia,in which X is halogens and R1 and R2 are organic radicals.
It is known from WO 01/32 666 A 1 (DE 199 53 048) that organic phosphorus compounds comprising halogens of the formulaeX(1-a)R2aP(OR1)2  I orX(2-a)R2aP(OR1)  II,in which X may be a halogen, R1 and R2 may be organic radicals and a may be the values 0 or 1, can be produced by reacting a compound of the formulaX(3-a)R2aP  III with a compound of the formulaR1OH  IVat 10 to 200° C. and atmospheric pressure. This gives a mixture V which comprises the compounds I and II. The compounds I and II are separated from one another. If compound I is the target product, compound II is returned to the synthesis step. If compound II is the target product, compound I is returned.
The disadvantage when producing compounds II where a=1 from compounds III where a=1 is that the reactant R1OH is not completely reacted when working atmospheric pressure. If the reaction products are worked up by distillation in order to isolate the target products, then the unreacted halogen-comprising organic phosphorus compounds II (a=1) react with the compounds R1OH to form hydrogen chloride and increase the amount of product which has to be returned. Furthermore, the target product II has to be purified from hydrogen chloride.